ORONO, Maine — A report of smoke appearing about 7:15 p.m. Tuesday in the basement at Margarita’s Mexican Restaurant on Mill Street prompted the temporary evacuation of about 20 employees and an unknown number of diners.

Lt. Scott Luciano of the Orono Fire Department said that an extensive search of the restaurant building, which consists of a basement and two stories, turned up no sign of fire. He speculated that the smoke might have been drawn in through the ventilation system from a nearby outdoor smoking area.

The restaurant, which Luciano said was closed for cleanup Tuesday night, is expected to reopen today.

Luciano said fire crews used thermal imaging cameras to check for hot spots, inspected ducts and opened up some of the building’s walls to see if the source of the smoke could be determined.

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He said the adjacent building, which houses Pat’s Pizza, also was searched.

Orono fire crews were assisted at the scene by members of the Old Town Fire Department and the University of Maine Volunteer Ambulance Corps, Luciano said. He said members of the Veazie Fire Department provided standby coverage from the Orono fire station. No injuries were reported in connection with the incident.